Domain check

domain-check

Platform-independent domain checker. Answers the binary question Available / Taken with high confidence (100% when all sources agree) and, for taken domains, returns the most relevant details inline: SSL certificate, server IP, expiration date.

MANDATORY READ — ANY DOMAIN-NAMING REQUEST

As the very first action — before generating, recommending, suggesting, scoring, or curating ANY domain names — you MUST Read references/naming_guide.md in full. Non-skippable. One Read tool call, ~3,300 words.

This rule fires on all of these triggers, not just on suggest:

• "schlag mir Domains vor", "suggest domains", "give me domain ideas"
• "good name for X", "guter Name für X", "creative domain names"
• "what should I call X", "wie soll ich X nennen"
• "Domain-Tipps", "domain tips", "naming ideas"
• bare suggest subcommand invocations
• any free-form follow-up where the user asks for a curated list of names

The guide is the single source of truth. The Python score_name() heuristics are a sanity helper, NOT a substitute for the guide. Skipping the guide produces generic voicebotify / cloudhub slop that doesn't match the user's actual project.

Workflow for any naming request:

1. Read references/naming_guide.md — non-skippable, before any candidate is written
2. Pick 2–3 patterns from the guide that fit the user's project (e.g. "AI phone bot" → Hybrid Neoclassic + Action-Verb + Made-up-Phonetic, NOT just voicebot+ify)
3. Hand-curate a candidate list using the guide's brainstorming techniques (semantic web, mood board, free association, grandma test, 1AM bar test)
4. Run bulk to check availability — suggest output is only a starting point, never the final list
5. Apply the don't-list (no hyphens, no digit substitutions, no false friends, no typo-squat distance ≤1)
6. Present 8–15 curated finalists with rationale + buy_links, not 200 raw heuristic outputs

Requirements

No dependencies. No venv. No pip/uv/pipx required.

The entire skill runs on the Python ≥ 3.11 standard library (needed for dict | None syntax and asyncio.to_thread). Module imports used by the skill: argparse, asyncio, dataclasses, datetime, hashlib, io, json, os, pathlib, re, secrets, socket, ssl, struct, sys, tempfile, time, typing, urllib. All stdlib.

If you run an exotic Python build without the SSL module, only the ssl subcommand will fail; the rest still works.

Quick Start

All commands are run from this skill's directory (the agent will cd there automatically). Same invocations on Linux, macOS, and Windows:

python3 scripts/domain_check.py check example.com
python3 scripts/domain_check.py bulk example.com example.org example.net
python3 scripts/domain_check.py ssl example.com
python3 scripts/domain_check.py resolve https://example.com/path

On Windows, use python instead of python3 if needed.

Subcommands

check <domain>

Single-domain check, JSON output.

For "Taken" the response contains:

• verdict: "Taken", confidence, summary
• expiration_date (ISO date) or expiration_note (e.g. "DENIC confirms the registration but does not expose the expiry date publicly (GDPR).")
• registrar, nameservers, ip_addresses
• ssl: { issuer, subject, valid_to, days_until_expiry, fingerprint_sha256, ip_address, matches_hostname, ... }
• evidence: [...] — list of all 5–6 sources with source/strength/reason

For "Available" a compact response: verdict: "Available", confidence, summary, evidence. No SSL/IP blocks (irrelevant).

For "Reserved" / "Unclear": verdict plus rationale in summary plus evidence for diagnosis.

bulk <d1> <d2> … OR --file <path> OR --stdin

Up to 8 domains in parallel. NDJSON output (one line per domain) — pipe-friendly. Alternatives:

• --format=json → a single JSON array
• --format=table → human-readable table

python3 scripts/domain_check.py bulk --file domains.txt --format=table
echo -e "example.com\nexample.org" | python3 scripts/domain_check.py bulk --stdin

ssl <hostname> [--port 443]

SSL certificate only. Returns issuer, subject, SAN, valid_from/to, days_until_expiry, SHA-256 fingerprint, protocol, cipher, and the effective IP of the TLS connection.

resolve <url-or-host>

Extracts the hostname from a URL and resolves IPv4 + IPv6, plus reverse DNS for the first 3 IPs. Accepts https://example.com/path, example.com:443, example.com.

What is the "TLD-aware decision tree"?

Whether a domain is "Available" or "Taken" depends on which sources are authoritative for the given TLD:

• gTLDs (.com, .net, .io, .ai, .app, .pro, .club, …): RDAP is mandatory under ICANN — RDAP no-object = 100% available.
• GDPR ccTLDs (.de, .eu, .at, .ch, .es, …): the registry typically redacts RDAP/WHOIS entirely. Here an authoritative DNS NS lookup against the registry NS (a.nic.de, x.dns.eu, …) yields a binary answer: NS records = registered, NXDOMAIN = available.
• Unknown / reseller TLDs: the WHOIS server is discovered live via whois.iana.org and cached persistently. If the response contains only disclaimers (no domain/registrar fields), the domain is treated heuristically as available.

Edge Cases

• IDN domains (münchen.de): automatically converted to Punycode (xn--mnchen-3ya.de).
• GDPR TLDs without expiry: expiration_date is null and expiration_note explains why. This is correct behaviour, not a bug.
• .ch/.li/.es: registry WHOIS port 43 is blocked for anonymous IPs. The authoritative DNS NS lookup is the primary source here.
• Rate limiting (DENIC, AFNIC, SIDN): bulk concurrency is capped at 8; on HTTP 429 a single retry with short backoff is attempted.
• IDNA failure: invalid IDN inputs fall back to lowercase ASCII — no crash.

Performance

• Single check: typically ~2–4 s (all 5 sources in parallel via asyncio).
• Bulk: 30 domains in ~10–15 s (concurrency 8, each domain again fans out per source).

Architecture (for maintenance)

scripts/
├── domain_check.py          # CLI entry point, argparse subcommands
└── _lib/                    # importable Python package
    ├── tld_classifier.py    # TLD → GTLD_FULL / CCTLD_DSGVO / CCTLD_OPEN / UNKNOWN
    ├── rdap.py              # RDAP client with IANA bootstrap cache (24h)
    ├── whois_client.py      # WHOIS socket + 30+ TLD patterns + IANA discovery + heuristic fallback
    ├── auth_dns.py          # native UDP DNS resolver (RFC 1035) for TLD registry NS
    ├── presence.py          # DNS A/AAAA, HTTP/HTTPS, TLS cert with CN/SAN match
    ├── verdict.py           # decision tree: Available/Taken with confidence
    └── orchestrator.py      # async fan-out + user-friendly final report

Other skills can import the library modules directly:

from _lib.orchestrator import check_domain
report = await check_domain("example.com")

Naming Guide & Suggestion

The skill also helps you come up with good names, not just check existing ones.

What makes a great domain name

Read references/naming_guide.md — a practical guide covering:

• The "type-once, no-spell-back" test
• Length sweet spots (top-100 sites average 6.2 chars)
• Phonetics: plosive consonants, vowel endings, alliteration, rhyme
• Naming patterns: real-word, compound, made-up, portmanteau, Hybrid Neoclassicism (Lumen, Nexus, GraphBase)
• TLD strategy with concrete matrix
• The AI-era twist: LLM citability, voice-agent discoverability
• Hard don't list: hyphens, digit swaps, false friends, typo-squats
• Real rebrand examples (Lyft, Flickr, Tumblr, Twilio…)
• A step-by-step 30-Minute Naming Workout to run before generating candidates

suggest <seed> --use-case <type>

Generate scored domain candidates from a seed keyword. Patterns: Greek/Latin roots, Hybrid Neoclassic, Suffix-Stack, Compound, Mutation, Action-Verb-Compound. Each candidate gets a 0.0–1.0 score from the heuristics in _lib/naming.py (length, syllables, phonetics, plosive starts, alliteration, trademark/typo-squat checks). Use cases: tech_startup, ai_tool, dach_service, indie_saas, creative, developer, ecommerce_de, consumer_app, open_source, agency_dach.

python3 scripts/domain_check.py suggest graph --use-case ai_tool --count 20
python3 scripts/domain_check.py suggest cloud --use-case indie_saas --check --check-top 5

The --check flag runs availability checks on the top candidates so you only see names that are actually buyable.

score <name>

Score a single bare name (no TLD) and see the heuristic breakdown — useful when you already have an idea and want a sanity check.

python3 scripts/domain_check.py score lumenforge

The scorer is a sanity helper, not the truth — strong real brands like zoom, slack, stripe all live below 0.8 because the heuristics penalise short or low-vowel names. Use the score to spot obvious red flags (hyphens, digits, hard clusters), not as a gatekeeper.

Resources

• references/naming_guide.md — what makes a great domain name (the creative side)